Heat treatment of metals



J. W. HARRIS HEAT TREATMENT OF METALS June 1 1926.

Filed NOV. 22, 1922 Patented June 1, 1926.

UNITED STATES PATENT OFFICE.

JONATHAN W. HARRIS, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERNELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OFNEW YORK.

Application filed November 22, 1922.

This invention relates to heat treatment of metals and more particularlyto the heat treatment of material containing two or more metals, one ofwhich would be harmed by an active oxidizing atmosphere and another ofwhich would be injured by an active reducing atmosphere. An example ofsuch a material is an electrical conductor of copper, covered with alayer of spirally wound wire or tape of a nickel-iron alloy to increaseinductance, the alloy requiring a heat treatment after being Wound uponthe conductor to increase its permeability. This invention originatedduring the development of the heat treatment of such an inductivelyloaded conductor.

An object of the invention is to provide a suitable atmosphere for useduring the heat treatment of material, such for example as that justmentioned, which cannot be subjected to the action of a reducing or tomore than a slightly oxidizing agent.

Another object is to provide means for permitting a compound conductorto be heat treated without resultant brittleness and without theproduction of oxide upon the surface of the materials.

Investigations have recently been in progress looking toward theimprovement of submarine telegraph cables. As a result of theseresearches it has been found that the speed of signaling over longsubmarine cables can be greatly increased by inductively loading thecable conductor with wire or tape of a certain nickel-iron alloy appliedas a spiral wrapping, the wrapped conductor being given a certain heattreatment in order to increase the permeability of the loading material.The loaded conductor preferably consists of a central cylindrical copperwire covered by a layer of contiguous strands or tapes of the samematerial having a spiral lay -The preferred method of applying the heattreatment to the loaded conductor is to pass it slowly through a furnaceand then through a cooling chamber. The alloy should first be brought toa temperature above the transition temperature, which is about 850 or900 C. and then allowed to remain at that temperature for a definiteperiod, which appears to be necessary to insure a uniforminolecularstructure, after which it should be cooled sl wly hrough HEAT TREATMENTOF METALS.

Serial No. 602,501.

the transition temperature and then further cooled at a rate betweenthat necessary to anneal and rates which would set up mechanicalstresses in the material when cold.

For a complete description of the alloy mentioned herein; the method ofpreparing it, its use as an inductive loading material and the manner ofapplying it to the conductor to be loaded, reference is made to thefollowing United States applications: G. WV. Elmen, 473,877, filed May31, 1921; O. E. Buckley, 492,725 and 492,7 26, filed August 16, 1921; G.W. Elmen, 557,928, filed May 2, 1922 and G. W. Elmen 602,287 filedNovember 20, 1922.

The invention is fully described in the following specification. Theaccompanying drawing is a diagram of the furnace and cooling chamber forapplying a heat'treatment to an inductively loaded conductor togetherwith means for supplying a desired atmosphere to the region about theheated conductor in accordance with the invention.

Referring to the drawing, a conductor 1 having a layer of wire or tapeof magnetic material spirally wound thereon, is slowly unreeled from thesupply reel 2, passed through the furnace 3 and the cooling chamber fand rewound upon the receiving reel 5. The furnace 3 is in two sections6 and 7 which have separate heating means 8 and 9 of difl erent heatingcapacity, such as electric resistance coils of difierent sizes. Thefurnace 6 is maintained at such a temperature, well above the transitiontemperature, that as it leaves this furnace, it is at or somewhat abovethe transition temperature. A second furnace or furnace section 7 ismaintained at or just above the transition temperature and is of such alen h that at the velocity with which the con uctor is moved, the latterwill be maintained at this temperature the required time. The coolingchamber 4, which is illustrated as a water jacket, cools the alloy at arate between that necessary for annealing and rates which \Wigld set upstresses in the material when co A tube 12 which may be in two or moresections, extends throughout the length of the furnace and coolingchamber, the portion within the furnace being of heat resisting materialsuch. as nickehand. this or similar material may be used for the sectiontlti . surethrough the pipe 11.

of the tube extending from the furnace to a point within the coolingchamber at which the temperature of the conductor is material- 1y lower'than when it leaves the furnace. The internal diameter ofthe tubepreferably not much greater than the external diameter of the tapedconductor. A jacket 10 surrounds the tube 12 between the furnace and thecooling chamber and may be supplied with any desired as under preshetube 12 is perforated within the jacket 10. The pressure at which thegas is supplied is dependent upon the rate at which the conductor ismoved through the tube 12 and the temper-' atures of the furnaces.

A heav coating of oxide upon the surface of the alloy of the tapedconductor after the heat treatment above described is highlyobjectionable. If the atmosphere surrounding the tape while it is hot isof. a reducingnature, a bri ht unoxidized surface is maintained on t etape and on the conductor. However, all copper wire of high conductivitywhich it is possible to obtain on the market contains some dissolvedcuprous oxide. At the temperature to which the conductor is heated, if areducing atmosphere such as hydrogen, for example, is maintained, thecopper oxide dissolved in the copper conductor becomesreduced, with theeffect that the copper of the conductor, both the central solidconductor and the tapes surroundin it, become embrittled. In order toavoi any embrittling of the copper conductor and yet maintain areasonably bright surface on the loading tape or wire, an atmosphere ofnitrogen is preferably employed. This is supplied through the pipe 11under a pressure which will produce a very small rate of flow. It flowsboth to the right and to the left through the tube 12 around the heatedconductor, escaping from the open ends of this tube. The passage of thegas to the right is relatively unimportant, the chief object being tokeep the conductor in this atmosphere until it has been materiallyreduced in temperature in the cooling chamber. The passage of the gas tothe left is of greater importance, an important function being to sweepfrom the tube harmful reducing or.

oxidizing gases, such as those which tend to be drawn in by the tapedconductor as it enters the tube 12, and those which may be produced inthe furnace by the action of heat upon foreign substances such, forexample, as traces of oil upon the conductor. This object could not beaccomplished by flowin the gas from left to rig t through the tu 12, inthe furnace, since any air drawn in with the taped conductor would becarried at once into a region of higher temperature, and, before itcould be swept out at the opposite ,end, would enter into unease?chemical combinations. Likewise, the in- ]l1-I10l18 effect of reducigases liberated by the heat within the tu 12 can be more eflectlvelyavoided by sweeping such gasesat once into a region of lowertemperature, than by attempting topass them through a region of the sameor higher temperature.

A further feature of the invention is the use of small amounts of oxygenmixed with the nitrogen. Oily or carbonaceous matter upon the loadedconductor in the furnace gives rise to a certain amount of reducingatmosphere which may react adversely on the copper conductor. If,however, a very small amount of ox gen is present, this tends to expenditself afiely in oxidizing such carbonaceous or r ucing material. Aslight tarmshm of the tape results from the presence of t is oxygen, butnot enough to be harmful, It is found that from .3 to 1% of oxygen isordinarily present in commercial: 1y prepared nitrogen, althoughoccasionally as 1 as 3% occurs. The former values are a out thosenecessary for the oxidizing of reducing material carried into thefurnace on the conductor and the latter value, while larger than desiredis not prohibited, so that it is not necessary to separately providechemically pure nitrogen and oxygen. The cost of the desired gas mixtureis thus kept at a low value. The amount of oxygen could of course bereduced if desired, if the velocity of the nitrogen stream through thetube 12 were increased, the sweeping action of the nitrogen stream thencarrying away a greater amount of any reducing atmosphere produced inthe furnace tfrom carbonaceous matter upon the conduc- While thisinvention was developed in connection with the heattreatment for conductors loaded with magnetic alloy, it is obvious that the invention isbroader than that in scope and this has been borne in mind in draftingthe appended claims.- For example one feature of the invention is theuse of certain gas or gases as described above, and it is within thescope of the invention to use such atmos here with or without the addedfeature of producing a constant flow of the gas or gases.

What is claimed is:

1 Means for heat-treating metallic'materlal comprising a heatingchamber, means to continually pass the metallic material into saidchamber. through an opening, and means for causing a substantiallynonoxidizing and non-reducing gas to pass continually into said .chamberand out through said opening at a rate high ,enou h to sweep back anyentering gas before it lies time to appreciably affect said metallicmaterial.

2. Means for heat-treating a wire or cable comprising a heating chamber,means for passing the wire or cable continually into said chamberthrough an opening, means for causing a liberation of gas of a reducingnature in said chamber, and means for causing gas to pass continuallyinto said chamber and out through said opening at a rate high enough tosweep back through said opening at least a portion of any gas of areducing nature liberated in said chamber before said reducing gas hastime to appreciably afl'ect said wire or cable.

3. Means for heat-treating an electric conductor comprising copper, saidmeans cognprising a heating chamber, means for feeding the conductor tosaid heating chamber through an opening, and means for causing gas topass into said chamber and out through said opening, said gas being of anature to prevent said copper from becoming embrittled under the actionof heat in said chamber.

4. Means for heat-treating a copper wire or cable comprising a heatingchamber, means for feeding the wire or cable into said chamber when thelatter is heated, and means for maintaining an atmosphere of gas in saidchamber of such a nature as to prevent the copper from becomingembrittled under the action of heat, as it would in the presence of.reducing gas.

5. Means tor heat-treating a metallic wire or cable comprising a heatingchamber,

means for feeding the wire or cable into said chamber, means forsupplying an atmosphere to said chamber comprising nonreducing andoxidizing gases, the latter sufficient only in amount to slightlyoxidize the surface of the wire or cable and unite with a portion atleast of any reducing substances produced from impurities upon said wireor cable by the heat, and means for causing a steady movement of saidatmosahere outward through said opening to sweep out reducing gas notacted upon by said 0x1- dizing gas.

6. Means for heat-treating a compound conductor comprising a copper"core upon which is spirally wound a layer of wire or tape of a magneticmaterial requiring heattreatment to increase its permeability and of anature to oxidize rapidly under such treatment in the presence ofoxygen, said heat-treating means comprising a heating chamber, means forfeeding the conductor to said chamber, means for supplying to saidchamber an atmosphere which will not cause said copper core to becomebrittle under the action 0 heat, and which has an oxidizing effect onlygreat enough to slightly oxidize the metallic surfaces and to assist ineliminatiiig reducing action upon the copper of agents liberated by heataction from impurities upon the metals.

i. Means for heat-treating a compound conductor comprising copper andmagnetic material, the latter requiring heat t'reatment to increase itspermeability and of a nature to oxidize rapidly under such heattreatment in an atmosphere rich in oxygen, said heattreating meanscomprising a heating chamber for applying such heat treatment'to theconductor, and means for maintaining a nonreducing and only slightlyoxidizing atmosphere in said chamber.

8. Means for heat-treating a compound conductor comprising a copper coreupon which is spirally wound wire or tape of magnetic material requiringa heat treatment to increase its permeability and of a nature to oxidizerapidly under such treatment in an atmosphere rich in oxygen, saidheat-treating means comprising a heating chamber for applying such heattreatment to the conductor and means for supplying to said chamber anon-reducing and only slight ly oxidizing atmosphere comprising nitrotooxidize rapidly under such' treatment inan atmosphere rich in oxygen,said heattreating means comprising a heating chamber for applying suchheat treatment to the conductor, and means for maintaining in saidchamber an atmosphere of commercially -prepared nitrogen which containsa slight amount of oxygen.

10. Means for heat-treating a compound conductor comprising a coppercore upon which is laid the material requiring heat treatment, and of anature to oxidize rapidly under such heat treatment in an atmosphererich in oxygen, said heat-treating means comprising a heating chamberfor applying such heat-treatment to the conductor, and means formaintaining an atmosphere of gas in said chamber of a nature to reventthe copper-from becoming emb rittle under mosphere consistingprincipally of nitrogen in said chamber to prevent the copper frombecoming embrittled under the action of heat and to prevent excessiveoxidation of the surfaces of the metals.

- 12. Means for heat-treating an electric conductor made in part atleast of copper, comprising a. heating chamber, means for passing theconductor contlnuously mto sald chamber through an opening, and meansfor causing gas to pass continually into said chamber and out throughsaid opening at a rate high enough to sweep back through said opening atleast a portion of any gas of a reducing nature liberated in saidchamber before said reducing gas has time to appreciably afi'ect saidconductor.

13. Means for heat-treating a compound conductor comprising copper andmagnetic material, the latter requiring heat-treatment to increase itspermeability and of a nature to oxidize rapidly under such treatment inan atmosphere rich in oxygen, said heattreating means comprising aheating cham her for applying said heat treatment to the conductor andmeans for causing a substantially non-oxidizing and non-reducing gas topass continually into said chamber and out through said opening at arate high enough to sweep into a region of lower temperature a portionat least of any gas of a deleterious nature liberated in said chamberbefore said deleterious gas has time to appreciably affect the materialsof said conductor.

14. Means for heat-treating a composite conductor comprising a pluralityof elements, each of which is deleteriously affected by reducing agentsat high temperatures but unaffected by slightly oxidizing agents, saidheat-treating means comprising a heating chamber, means for passing saidconductor through said chamber in the presence of a reducing agent, andmeans counteracting the action of said reducing agent.

15. Means for heat-treating a composite conductor comprising a,plurality of elements, each of which is deleteriously affected byreducing agents at high temperatures but unaifected by slightlyoxidizing agents, said heat-treating means comprising a heating chamber,means for passing said conductor through said chamber in the presence ofa reducing agent. and means for supplying an inert gas to said conductorto prevent said deleterious action of said reducing agent.

In witness whereof, I hereunto subscribe my name this 21st day ofNovember A. 1)., 1922. 4

JONATHAN W. HARE-I

